Neutrophils are critical for host defense against microorganisms and are the cellular mediators of acute inflammation. Neutrophils share with other cells signal transduction pathways, many of which are regulated by ras-related GTPases, including the rho proteins recently shown to regulate the actin cytoskeleton. These molecular switches are targeted to membranes by a series of post-translational modifications that include prenylation, proteolysis and carboxyl methylation. We have established that reversible rho protein carboxyl methylation is associated with neutrophil activation and may regulate GTPase function. We now propose to clone the gene for human myeloid prenylcysteine-directed carboxyl methyltransferase (pcCMT) and to identify proteins that regulate or are regulated by neutrophil rho proteins and to determine the role of carboxyl methylation in these interactions. The lab will be used for PCR, ELISA, DNA sequencing (automated), ultracentrifugation, autoclaving, Recombinant DNA techniques, and laminar flow hoods.